Climate change is likely to be a factor in the extreme weather that has hit much of the UK in recent months, the Met Office's chief scientist has said.
Dame Julia Slingo said the variable UK climate meant there was "no definitive answer" to what caused the storms.
"But all the evidence suggests there is a link to climate change," she added.
"There is no evidence to counter the basic premise that a warmer world will lead to more intense daily and hourly rain events."
More than 130 severe flood warnings - indicating a threat to life - have been issued since December. In contrast, there were only nine in the whole of 2012.
More than 5,000 properties have been flooded over this period, although the Environment Agency says investment in flood defences over the past decade has protected a further 1.3 million properties.
Speaking ahead of the launch of a Met Office report - produced by the Centre of Ecology and Hydrology - into recent climatic events, Dame Julia said the UK had seen the "most exceptional period of rainfall in 248 years".
Unsettled weather at this time of year was not unexpected - but the prolonged spell of rain, as well as the intensity and height of coastal waves, was "very unusual".
"We have records going back to 1766 and we have nothing like this," she said. "We have seen some exceptional weather. We can't say it is unprecedented but it is exceptional."
The report links the recent extreme weather in Europe and North America to "perturbations" in the North Atlantic and Pacific jet streams, partly emanating from changing weather patterns in South East Asia and "associated with higher than normal ocean temperatures in that region".
"The attribution of these changes to anthropogenic [caused by humans] global warming requires climate models of sufficient resolution to capture storms and their associated rainfall," it says.
"Such models are now becoming available and should be deployed as soon as possible to provide a solid evidence base for future investments in flood and coastal defences."
David Cameron has said the UK must be prepared for more extreme weather.
At Prime Minister's Questions last month, Mr Cameron said he "suspected" that the recent storms to batter the UK and the extreme weather in North America were connected to global temperature changes - an argument challenged by some Conservative MPs and peers.
He subsequently clarified the remarks, saying that although "you can't point to one weather event and say that is climate change", many scientists were talking of a link between the two.
"The point I was really trying to make is, whatever you think - even if you think that (climate change) is mumbo-jumbo - because these things are happening more often, it makes sense to do all you can to... prevent these floods affecting so many people and that is exactly what we are doing."
Friends of the Earth climate campaigner Guy Shrubsole said this assessment was a "warning sign that cannot be ignored".
"By appointing an environment secretary who doesn't take climate change seriously this government has turned its back on the science and cut flood defence spending when it should be cutting emissions."